Various photometers are commercially available for measuring the light absorbance of liquid samples in microtitration plates or other sample-holding vessels. One example of such equipment is the MR 600 Microplate Reader marketed by Dynatech Laboratories, Incorporated of Alexandria, Va.
Known photometers of the foregoing type do not read or measure the size or diameter of hemagglutination clots (also called hemagglutination buttons) or other masses of particulate or solid material in the bottom of the sample-holding well or other vessel. Furthermore, known photometers of the foregoing type do not indicate variations of optical density of the button or other solid mass throughout its cross section. As a result, known photometers of the foregoing type do not provide the measurements necessary for interpreting a variety of different assays such as hemagglutination tests, latex agglutination tests, and complement fixation tests.
Prior to this invention, the size and pattern of such hemagglutination buttons and other solid masses were customarily determined by visually inspecting the button or mass in the microtest well or other sample-holding vessel. Such visual inspection, however, is time consuming and subject to erroneous and nonuniform interpretation.